Abstract: A three part enclosure system protects a sensor package and its connection to a main seismic cable. The enclosure system further anchors the sensor package to the cable. The enclosure system includes a combination takeout and anchor, molded to the cable; an opposing anchor; and a substantially cylindrical enclosure body or protective cover, adapted to contain, locate, and protect the sensor package and pigtail wire connections.

Abstract: A seismic coupling device for geophones firmly couples seismic sensors to the sea floor. The structure is open for the free flow of sea water and mud through the structure so that it moves freely through the sea water and solidly embeds itself in the ocean bottom. It is preferably made of a corrosion resistant metal, such as stainless steel, which also resists bending forces on the cable take-up reel, and provides further mechanical protection for sensor components enclosed within. A segmented ring at each end clamps around the protective enclosure which encloses the sensor package, and a further pair of segmented rings inside the ends clamps around the enclosure. A plurality of axially oriented longitudinal bars couple to the rings to form a squirrel cage around the enclosure.

Abstract: A hydrophone streamer including a central member running substantially the length of the streamer with a strength member and a plurality of conductors has formed therein space adapted to receive a plurality of a spaced apart pairs of collars, a cylindrical chamber wall between each of the pairs of collars defining a chamber, and one or more hydrophones within the chamber. The chamber wall has one or more opening through it for the free passage of sea water into the chamber, thereby shielding the hydrophones from extraneous noise while exposing the hydrophones to a seismic signal conducted by the sea water surrounding the streamer.

Abstract: An arcuate or flat ferroelectric sensor is incorporated in a seismic streamer. The structure comprises two half-cylinders which are mounted together around a cable. The half-cylinders are coupled together by bolts or pins or any other appropriate means. Each half-cylinder defines a well into which a sensor is mounted. With the sensor in place, the structure is covered over with a sound-transparent material to receive an acoustic signal into the sensor. Electrical leads from the sensor are directed through ports in the half-cylinders, and the leads are connected together to provide a composite sensed signal to the cable in analog form. The sensor in each half-cylinder is a single element hydrophone that, when connected to a sensor in a complementary half cylinder in series or in parallel, forms an acceleration cancelling hydrophone.

Abstract: An arcuate or flat ferroelectric sensor is incorporated in a seismic streamer. The structure comprises an interior cable, a surrounding woven strength member, an overlying foam floatation layer, and an enclosing jacket. One or more elongate channels are formed in the overlying floatation layer, and one or more hydrophones are mounted in the channel(s). The elongate channel enlarges the acoustic aperture for the reception of seismic signals.

Abstract: A variable length data packet in a seismic system includes a fixed-length data portion and a variable-length data portion, the amount of data in the variable-length portion depending on the number of active channels. The data packet identifies the number channels which are in operation in the system, which may be the same or fewer than the number of installed channels. This signals the central recorder as to the length of the block of data in the data packet which includes seismic data. This feature permits the scaling of the system to accommodate varying numbers of channels, without reconfiguring the system. In another aspect, a method of sending data in a data system having a plurality of installed channels includes the steps of determining the number of active channels; assembling a packet of data comprising a fixed-length field and a variable-length field, the number of data bytes in the variable-length field being a function of the number of active channels; and sending the packet of data.

Abstract: A vertical hydrophone cable includes a support cable, a plurality of hydrophones, and an equal number of delay elements which are tuned to provide synchronization between the seismic and electrical signals. A number of such vertical hydrophone cables are provided. In operation, the vertical array provides a method of seismic exploration comprising the steps of deploying the plurality of vertical hydrophone cables with the integral delay elements, generating a seismic signal, and receiving reflected return signals at the plurality of hydrophones with synchronism between the electrical and sound signals, so that the vertical cable functions in the manner of a traveling wave antenna.

Abstract: A device for joining the parted ends of a rope member is provided. The device comprises blocks that are epoxied to the ends of the rope member and a threaded sleeve to thread onto one of the blocks. The invention also provides a method of joining the parted ends of a rope member including the steps of epoxying a block to each end to be joined to form a splice and coupling a threaded sleeve to one of the blocks while securing the other block within the sleeve.

Abstract: A connector for fiber optics provides a means for eliminating a receiver in a redundant communications channel. The connector receives at least two optical fibers in side-by-side contact and positions the optical fibers in close proximity but not abutting contact with a photo detector imbedded in the connector. The connector further provides a method and a system for redundant data communications.

Abstract: A technique and a system provide control and monitoring of devices external to a marine seismic streamer by segmenting the conductor to which the external devices are coupled. The module which connects sections of the seismic data telemetry cable is modified to include a switch. The switch is controlled by a command signal on the seismic data telemetry cable to segment the twisted pair bus into a plurality of dedicated busses, each dedicated to a subset of the external devices, such as one or two such devices. In this way, the external devices can be communicated with in parallel, rather than in series as in conventional systems.

Abstract: An active element in a hydrophone includes a piezoelectric hydrophone crystal mounted to a backing plate. The piezoelectric crystal may be divided into separate segments. If so segmented, the polarities of the segments are oriented in the same direction. Whether or not segmented, the center portion or segment of the crystal is in abutting contact with a motion limiter, which acts as a spring between the piezoelectric crystal and the casing surrounding the crystal and backing plate. The portions or segments or the crystal are connected to electrical signal leads with the minimum amount of solder necessary to ensure secure electrical and mechanical coupling, thereby reducing the effects of the solder connection on the stress flux profile in regions of the crystal close to the solder.

Abstract: A system for testing a group of hydrophones includes (a) a tank having a nozzle adapted for attachment of a streamer jacket; (b) a harness reel inside the tank for reversibly retaining a group of hydrophones; (c) fluid passage means into the tank for introducing and withdrawing fluid into and out of the tank; (d) an oscillating pump in fluid communication with the tank to introduce a time varying pressure pulse in the tank; (e) a reference hydrophone inside the tank; (f) electrical coupling means to couple a hydrophone signal from the group of hydrophones and the reference hydrophone to a central processing unit; and (g) means for comparing the hydrophone signal of the reference hydrophone to the hydrophone signal of the group of hydrophones.

Abstract: An active element in a hydrophone includes a piezoelectric hydrophone crystal mounted to a backing plate. The piezoelectric crystal may divided into separate segments. If so segmented, the polarities of the segments are oriented in the same direction. Whether or not segmented, the center portion or segment of the crystal is supported in part by a center pin at its center. Thus, in the presence of a downward pressure, the end portions or segments develop a concave flexure and the center segment, due to the center pin support, develops a convex flexure. With this reverse flexing phenomenon, the center portion segment develops an electrical signal of opposite polarity from those of the end segments. By carefully selecting the areas of the end segments, and electrically coupling the segments so that the harmonics of the various segments are added out of phase, the distortion introduced the harmonics of the various phases subtract.

Abstract: A hydrophone structure comprises a hydrophone casing within which is mounted a conductive substrate. Sound pressure signals are conducted into the interior of the substrate, on which are mounted piezoelectric crystals on the exterior of the substrate. The volume between the casing and the substrate is nearly filled with a fluid, preferably oil. One or more bubbles of air remain in the volume between the casing and the substrate to permit vibration of the substrate and consequently the piezoelectric hydrophone element.

Abstract: A hydrophone transducer is prepared by depositing a piezoelectric material upon a conductive substrate or support structure, and then etching the material into selected regions or segments. The center segment, which provides most of the fundamental signal, is polarized in a first direction by the introduction of a polarizing voltage. The end segments are polarized in the opposite direction by the imposition of a polarizing voltage in the opposite direction. The conductive substrate then serves as one terminal of the output of the hydrophone while the upper surfaces of the segments together serve as the other terminal. The relative strengths of the signals from the segments may tailored by adjusting the areas of the segments.

Abstract: A system and method provide a low distortion hydrophone. A first known piezoelectric element is mounted so as to receive a pressure signal. A second piezoelectric element is provided with a means of receiving and enhancing the same pressure signal. Since a piezoelectric element is a capacitor, another capacitor is coupled in parallel with the second element to serve as a divider. The output voltage of the combination of the two elements is taken as the difference between the positive terminals of the two elements. Thus, the effect of the pressure enhancer and capacitance divider is to provide a difference in potential between the fundamentals from the two elements, while rendering the amplitude of the second harmonics equal. The two equal second harmonics cancel each other out at the output terminals, while retaining a useful fundamental for further signal processing.

Abstract: A modular subsea control pod assembly having a retrievable pod assembly and a receptacle assembly. The retrievable pod assembly has a stab block and at least one function port having an opening in the stab block. The retrievable pod assembly includes a pod gate which is adapted to move between a first position in which the pod gate covers the function port opening and a second position in which the pod gate does not cover the function port opening. The receptacle assembly includes a receptacle base module adapted to receive the stab block and a receptacle function port adapted to be connected to a blowout preventer hydraulic operator. The receptacle assembly includes a receptacle gate which is adapted to move between a first position in which the receptacle gate covers the receptacle function port opening and a second position in which the receptacle gate does not cover the receptacle function port opening.

Abstract: A digital marine seismic system employes a plurality of data acquisition control modules which simultaneously digitize analog seismic signals. The control modules also are selectably addressable in that each module is uniquely programmed to respond only to a particular control word. The system allows a large number of channels, such as 480 channels, on a simple transmission system, such as a twisted pair of wires. Each module includes a power switch to sequentially apply power to downstream modules. Selective addressing of the switches allow testing of specific modules for power malfunctions.

Abstract: Disclosed is a cable leveling device for a seismic marine cable. The cable leveling device features a motor which controls diving planes by way of direct mechanical linkage. The motor is controlled by a stored program digital processor connected in a closed loop feedback circuit. Optical reflective sensors are employed in the feedback loop to monitor the position of the mechanical linkage to directly determine the angle of the diving planes. A telemetry unit is provided to telemeter data from the cable leveling device to shipboard via the marine cable.

Abstract: Sensors mounted in detachable modules are located at selected positions along a cable, such as one used in marine seismic exploration, adapted to be towed behind a vessel in a body of water. The sensors are selectively addressable, either individually or as a group, by coded signals sent through the cable. When addressed, the sensors provide readings of the earth's magnetic field vector. The readings are used to provide an indication of the position of the sensors and thus the cable relative to the towing vessel. Cable depth readings may also be made by the sensors.